1. Field of the Invention
The present invention relates to a step type mask aligner, usable for manufacturing semiconductor devices, of a step-and-repeat alignment and exposure type. According to the present invention, the most desirable mode of the shot arrangements is selected with the use of a microprocessor.
2. Description of the Prior Art
A so-called stepper type alignment and exposure apparatus is known, wherein a circuit pattern on a reticle or mask is projected onto a small area of silicon wafer having a photoresist surface through a reduction projection optical system, and then the wafer is stepped to be exposed to the same pattern at the next area; this cycle is repeated. Where the projection optical system has such a small exposable area that a pattern for only one chip can be projected in one shot to the wafer, as in some of conventional steppers, the arrangement, that is, the places and order of the shots for the wafer, is determined indiscriminately for all wafers with no problem. However, the recent stepper which has a larger exposable area, i.e., the larger field of image makes it possible that one shot exposes plural chip patterns. In such a case, there is a problem that trial and error must be repeated to obtain the proper arrangement of shots from the standpoint of productivity.